A cockroach of mass m runs anticlockwise around the rim of a circular disc of radius R having moment of inertial I mounted on a frictionless vertical axis initially at rest. The speed of the cockroach with respect to the ground is v, whereas the disc turns clockwise with angular speed ω. The cockroach suddenly notices a bread crumb on the rim and, of course, stops immediately with respect to the disc. What is the angular speed of the disc after the cockroach stops?

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